When people do a special warm-up exercise, regular active folks get more tired, but top runners don't get any more tired—showing that your past exercise habits change how your muscles react.

Doing single-muscle exercises first makes you tired, so you can build muscle with lighter weights on bigger exercises.

Doing a special warm-up before lifting weights lets you finish your workout faster while still building just as much muscle.

Two different ways of lifting weights—pre-exhaustion and traditional—both help you get stronger and last longer during exercise about the same amount.

For top runners, doing 50 knee exercises in a special machine doesn't make their leg muscles get tired in a way that changes how quickly they fatigue, so it doesn't really affect their muscle tiredness after the workout.

When you do exercises back-to-back with little rest (pre-exhaustion training), it feels harder than doing exercises with normal rest breaks (traditional training).